Most of the other forum members either won't oppose longer lifetimes (every cert vendor would be happy) or will bow to the only two companies that matter.
And I really hope you are wrong that it will not get reversed. (I hope I am wrong about the above, but I doubt it.)
When the Internet breaks, people die. It's all fun and games to talk about hypothetical security problems that you aren't actually solving as an excuse to make the Internet incredibly transient and fragile, but it has a real human cost.
Right now, over 80% of organizations have outages do to a certificate issue every year. That's really bad, and already due to the CA/B's poor decisionmaking. But at the existing certificate lifetimes, at least it's predictable. Now the CA/B wants to multiply the possible problem occurrences by a factor of ten. And an organization can't even just be concerned with their own certificates, because any layer of their stack's software or infrastructure having a certificate error can have downstream effects.
The reason I believe this change will be undone, is because ultimately it will have to. It will be so obviously wrong if it goes into effect that people opposed to undoing it will get removed from the decisionmaking until it is undone.
If an org is tech-forward enough to have bothered setting up HTTPS for internal use cases on their own initiative, just because it was good for security, then they're not going to have major problems adapting to the 47-day lifetime. The orgs that will struggle to deal with this are the ones that did the bare minimum HTTPS setup because some external factor forced them to (with the most obvious candidate being browsers gradually restricting what can be done over unencrypted HTTP). Those external factors presumably haven't gone anywhere, so the orgs will have to set up private CAs even if they'd rather not bother.